3.7-Billion-Year-Old Rock Structures Formed by Tectonics, Not Life

10/17/2018

Scientists reevaluated evidence of life in 3.7-billion-year-old rock structures using improved imaging techniques and determined they were of geological origin, not biological origin as previously thought. Until the recent study, the structures were considered the earliest evidence for life on Earth.

The morphology, layering, mineralogy, chemistry, and geological context of the structures were originally attributed to the formation of microbial mats in a shallow marine environment 3.7 billion years ago at the start of Earth’s rock record. Previous studies on the rock samples employed millimeter scale information using laser ablation analysis to determine the origin of the formations.

In the more recent study, a team of scientists used micrometer x-ray florescence analysis at the National Synchrotron Light Source II (NSLS-II) to reexamine the rock structures. The Submicron Resolution X-ray (SRX) beamline revealed crucial new evidence based on the elemental make-up of the rock structures. This evidence supported the conclusion that the rock formations are of non-biological origin.

References

A. Allwood, M. T. Rosing, D. T. Flannery, J. A. Hurowitz, C. M. Heirwegh. “Reassessing evidence of life in 3,700-million-year-old rocks of Greenland.” Nature 563, 241 (2018) [DOI: 10.1038/s41586-018-0610-4]